1. Field of the Invention
The present invention relates to improvements in a lock-up torque converter for automatic transmissions in use for automotive vehicles.
2. Description of the Prior Art
In recent years, a torque converter with a lock-up mechanism has been proposed and put into practical use in order to further effectively transmit torque of an internal combustion engine to an automatic transmission in an automotive vehicle. A typical lock-up torque converter is disclosed, for example, in Japanese Utility Model Provisional Publication No. 57-100653. The lock-up torque converter includes a torsional damper through which a crankshaft of the engine is connected to a converter cover of the torque converter for absorbing the impact force due to the fluctuation of the engine torque.
However, with such a lock-up torque converter, since only the torsional damper is directly connected to the crankshaft during a lock-up condition, the inertial mass which should be directly applied to the crankshaft becomes short. Accordingly, the fluctuation of the engine speed is not sufficiently absorbed and increases a torsional vibration of the crankshaft and the noise in a passenger compartment.